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Some surveys show that a lot of people believe that the glare from snow causes snow-blindness. Yet, wearing dark glasses or not, they find themselves suffering from headaches and watering eyes, and even snow-blindness, when exposed to several hours of "snow light". The United States Army has now determined that glare from snow actually does not cause snow-blindness in troops in snow-covered country. Rather, a man’s eyes frequently find nothing to focus on in a broad expanse of a wide snow-covered territory. His gaze, in consequence, continually shifts and jumps back and forth over the entire landscape in search of something he can look at. Finding nothing to focus on, hour after hour, the eyes never stop searching, and the eyeballs will become sore and eye muscles will ache. Nature reduces this uncomfortable feeling by producing more and more fluid which covers the eyeball. The fluid covers the eyeball in increasing quantity until vision becomes increasingly unclear. The result may be total, even though temporary, snow-blindness. Experiments led the Army to a simple method of overcoming this problem. A small group of soldiers will be sent ahead of a main body of troops. They are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape. Even these soldiers themselves throw lightweight, dark colored objects ahead, on which they, too, can focus. The men following them can then see something. Their gaze is arrested. Their eyes focus on a bush and, having found something to see, stop searching the snow-blanketed landscape. By focusing their attention on lone object at a time, the troops can cross the snow-covered wilderness without becoming hopelessly snow-blind or lost. In this way the problem of crossing a solid white territory is overcome. People will have sore eyeballs when crossing snow-covered territory because ______.
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Large animals living in the desert have developed a number of adaptations for reducing the effects of extreme heat. One adaptation is to be light in color, and to reflect rather than absorb the sun’s rays. Desert animals also depart from other animals’ normal practice of maintaining a constant body temperature. Instead of trying to keep down the body temperature deep inside the body, which would involve the loss of water and energy, large desert animals allow their temperatures to rise to what would normally be fever height, and temperatures as high as 46 degrees Celsius have been measured in grant’s gazelles. The over-heated body then cools down during the cold desert night, and indeed the temperature may fall unusually low by dawn, as low as 34 degrees Celsius in the camel. This is an advantage since the heat of the first few hours of daylight is absorbed in warming up the body, and an excessive buildup of heat does not begin until well into the day. Another strategy of large desert animals is to tolerate the loss of body water to a point that would be fatal for non-adapted animals. The camel can lose up to 30% of its body weight as water without harm to itself, whereas human beings die after losing only 12%-13% of their body weight. An equally important adaptation is the ability to recover this water loss at one drink. Desert animals can drink massive volumes of water in a short time, and camels have been known to drink over 100 liters in a few minutes. A person who severely loses water, on the other hand, cannot drink enough water for recovery at one session, because the human stomach is not sufficiently big and because a too rapid mixing of the body liquid with water causes death from water intoxication. The tolerance of water loss is of obvious advantage in the desert, as animals do not have to remain near a water hole but can obtain food by searching quite a few distant places. Desert-adapted animals have the further ability to feed normally when extremely thirsty: it is a common experience in people that appetite is lost even under conditions of moderate thirst. What does the author imply regarding large desert-adapted animals
Large animals living in the desert have developed a number of adaptations for reducing the effects of extreme heat. One adaptation is to be light in color, and to reflect rather than absorb the sun’s rays. Desert animals also depart from other animals’ normal practice of maintaining a constant body temperature. Instead of trying to keep down the body temperature deep inside the body, which would involve the loss of water and energy, large desert animals allow their temperatures to rise to what would normally be fever height, and temperatures as high as 46 degrees Celsius have been measured in grant’s gazelles. The over-heated body then cools down during the cold desert night, and indeed the temperature may fall unusually low by dawn, as low as 34 degrees Celsius in the camel. This is an advantage since the heat of the first few hours of daylight is absorbed in warming up the body, and an excessive buildup of heat does not begin until well into the day. Another strategy of large desert animals is to tolerate the loss of body water to a point that would be fatal for non-adapted animals. The camel can lose up to 30% of its body weight as water without harm to itself, whereas human beings die after losing only 12%-13% of their body weight. An equally important adaptation is the ability to recover this water loss at one drink. Desert animals can drink massive volumes of water in a short time, and camels have been known to drink over 100 liters in a few minutes. A person who severely loses water, on the other hand, cannot drink enough water for recovery at one session, because the human stomach is not sufficiently big and because a too rapid mixing of the body liquid with water causes death from water intoxication. The tolerance of water loss is of obvious advantage in the desert, as animals do not have to remain near a water hole but can obtain food by searching quite a few distant places. Desert-adapted animals have the further ability to feed normally when extremely thirsty: it is a common experience in people that appetite is lost even under conditions of moderate thirst. The word "maintaining" in line 3 of the first paragraph is closest in meaning to ______.
An increase in free parks in Shanghai might be pleasant, but they bring with them their own problems. There are already 122 free parks for citizens to enjoy. But visitors are often hassled by beggars and fortune-tellers, and put off by the smell of urine left behind by someone using the grass as a toilet. Law and order in free parks are also worrying the city’s park operators. They couldn’t take any mandatory measures on those who do indecent things in parks except to try to persuade them to stop according to local regulations on park operations, which were laid out many years ago and many parts are not in line with the need for maintenance of the increasing number of free parks. Patrols could be introduced to help park managers. On April 1,2005, Shanghai opened 23 new free parks, bringing the total number of such parks to 122. A lack of cash has also hindered park operations. The local government has allowed for subsidies to cover the cost of not charging for tickets, but attendance is often more than expected, adding to maintenance and security costs. Many parks manage to be self-supporting by running businesses such as convenient stores and cafeterias. Some also rent out areas to companies who want to do outdoor promotions. But the bottom line is that parks should be comfortable places for visitors and should not be turned into outdoor markets. As well as not charging for tickets, parks are cutting back on staff, having a few staff members for daily operations. Most construction and maintenance jobs are commissioned to enterprises through public bidding so as to evaluate costs in a transparent and economical way. So far, more than 12,000 citizens are working as volunteers to help with park operations in Shanghai. Shanghai has spent more than 3 per cent of its GDP on environmental protection in recent years. Its heavy expenditure in landscaping also paid off as it won the "National Garden City" award last year. Shanghai’s goal is to increase its green area to 12 square metres per capita. It now has more than 17 million permanent residents. Which of the following is NOT true according to the passage
An increase in free parks in Shanghai might be pleasant, but they bring with them their own problems. There are already 122 free parks for citizens to enjoy. But visitors are often hassled by beggars and fortune-tellers, and put off by the smell of urine left behind by someone using the grass as a toilet. Law and order in free parks are also worrying the city’s park operators. They couldn’t take any mandatory measures on those who do indecent things in parks except to try to persuade them to stop according to local regulations on park operations, which were laid out many years ago and many parts are not in line with the need for maintenance of the increasing number of free parks. Patrols could be introduced to help park managers. On April 1,2005, Shanghai opened 23 new free parks, bringing the total number of such parks to 122. A lack of cash has also hindered park operations. The local government has allowed for subsidies to cover the cost of not charging for tickets, but attendance is often more than expected, adding to maintenance and security costs. Many parks manage to be self-supporting by running businesses such as convenient stores and cafeterias. Some also rent out areas to companies who want to do outdoor promotions. But the bottom line is that parks should be comfortable places for visitors and should not be turned into outdoor markets. As well as not charging for tickets, parks are cutting back on staff, having a few staff members for daily operations. Most construction and maintenance jobs are commissioned to enterprises through public bidding so as to evaluate costs in a transparent and economical way. So far, more than 12,000 citizens are working as volunteers to help with park operations in Shanghai. Shanghai has spent more than 3 per cent of its GDP on environmental protection in recent years. Its heavy expenditure in landscaping also paid off as it won the "National Garden City" award last year. Shanghai’s goal is to increase its green area to 12 square metres per capita. It now has more than 17 million permanent residents. Free Parks are cutting back on staff because ______.
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